DESIGN OF WATER HOLDING BULKHEADS FOR COAL MINES

ABSTRACT: Water control has been and remains a fundamentally important aspect of underground coal mine design and operation worldwide. Mining in the vicinity of large bodies of water, below a worked out coal seam or under confined aquifer or abandoned water logged workings is always fraught with the possibility of the danger of inundation. Inrush control is now part the Fatal Hazard Protocols which is a risk based process in all operations. In modern Australian underground coal mines, in which panel layouts have been extended and production rates are approaching 10 Mtpa, there is much focus on the control of water inflows. Flooding of mine workings can cause deterioration of roadways as was evidenced at Broadmeadow Mine in 2008 soon after the water receded due to a sudden reduction or pore water pressure, mobilisation of joints/cleats and swelling of clay layers in coal measures. Ventilation seals are primarily used in underground coal mines to isolate abandoned or worked out areas. However these seals are often required to impound large volumes of water to control the hazard mostly at the inbye end of longwall operations and in natural valleys. A systematic approach is required for the design of bulkhead seals including consideration of the longevity of building materials, quality control during construction and methods to monitor performance of the retention system. In recent years it has become accepted practice to use numerical methods to provide engineering ratings for engineerin